A conventional general driving-operation assist estimates a moving trace of a vehicle corresponding to a steering angle of a steering wheel for backward movement of the vehicle by a steering sensor for detecting the steering angle of the steering wheel. When a vehicle moves backward, an image of a rear or side-rear field of view photographed by a camera is displayed and moreover, when the steering wheel is operated, a moving trace of the vehicle estimated correspondingly to the steering angle of the steering wheel is superimposed on the image of the rear or side-rear field of view. According to the assist, driving operations by a driver will be performed as described below. That is, a driver moves a vehicle to a place where the vehicle can be probably parked while fixing the steering wheel of the vehicle. Then, at the place, the driver finds a steering angle capable of moving the vehicle to a space for parking the vehicle without operating any steering wheel while confirming a vehicle-moving trace estimated by operating the steering wheel. Then, by moving the vehicle backward toward a parking space while keeping the steering angle, parking is theoretically completed.
A conventional example of the above driving-operation assist is disclosed in the official gazette of Japanese Patent Laid-Open No. 1-14700.
However, to park a vehicle by using the above assist, it is necessary to find a place where the vehicle can be moved to a parking space and then determine a steering angle at which the steering wheel is fixed. To master these operations, skill is necessary. Moreover, when the size of a vehicle to be driven is changed, a sense differs. Therefore, the driving know-how accumulated during skill is not greatly useful.
Incidentally, to park a vehicle, it is generally difficult to complete parking operations while keeping a steering angle of a steering wheel constant from start of the parking operations except a case in which there is no obstacle nearby. For example, to perform parallel parking, a driver first moves a vehicle backward by turning the steering wheel in a proper direction while moving the vehicle to a place for parking the vehicle from a parking-operation start position and then, moves the vehicle to a target place by inversely turning the steering wheel when the vehicle properly moves backward. That is, in case of taking parallel parking as an example, it is difficult to park a vehicle while keeping a steering angle of a steering wheel constant.
Moreover, as for a conventional assist, if a driver slightly moves the steering wheel of a vehicle, a moving route of the vehicle re-estimated by the slight steering-angle change is displayed. Therefore, the driver may be confused.
That is, as for a conventional driving-operation assist, a driver cannot intuitively find a place where a vehicle can be easily moved to a parking space at a glance while confirming an image obtained by synthesizing the parking space, a state around the space, and a route for guiding the vehicle to the parking space.